OPNETWORK2003 1540 Vukadinovic final editedljilja/ENSC835/Fall03/News/Presentations/talk... · Title: OPNETWORK2003_1540_Vukadinovic_final_edited Author: ljilja Created Date: 9/19/2003

Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties.

GPRS

Session 1540

Discrete Event Simulation for R&D

Copyright © 2003 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 2

1540 GPRS

Mobile Application Part protocolimplementation in OPNET

Vladimir Vukadinovic and Ljiljana Trajkovic{vladimir, ljilja}@cs.sfu.ca

Communication Networks Laboratoryhttp://www.ensc.sfu.ca/cnl

School of Engineering ScienceSimon Fraser UniversityVancouver, BC, Canada


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Roadmap

§SS7 protocol stack and MAP§GPRS OPNET model§MAP implementation§HLR and SGSN node models§ Impact of MAP on the GPRS attach procedure§Conclusions


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Overview

§Mobile Application Part (MAP) protocol resides on top of theSignaling System 7 (SS7) protocol stack.§ In General Packet Radio Service (GPRS) networks, MAP

protocol supports signaling exchanges with:§Home Location Register (HLR)§ Equipment Identity Register (EIR).

§We implemented the MAP protocol as a part of an GPRSOPNET model.§The MAP implementation provides signaling between Serving

GPRS Support Node (SGSN) and HLR.§We evaluated the impact of the MAP protocol overhead on the

duration of GPRS attach procedure.


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§SS7 is an out-of-band signaling system for:§ Public Switched Telephone Networks (PSTNs)§ Public Land Mobile Networks (PLMNs).

§ It defines procedures for:§ connection setup, management, and tear down§ exchange of billing and routing information§wireless roaming§mobile subscriber authentication.

Signaling System 7 (SS7)


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SS7 protocol stack

§SS7 protocol stack consists of four layers.§Three lowest levels are combined into one set of protocols,

called the Message Transfer Part (MTP).§MTP is split into layers 1 through 3.

§Layer 4 consists of:§ Signaling Connection Control Part

(SCCP)§ Transaction Capabilities Application

Part (TCAP)§ Telephone User Part (TUP)§ ISDN User Part (ISUP)§ Intelligent Network Application

Protocol (INAP)§ EIA/TIA interim standard 41 (IS41)

EIA/TIA: Electronic Industries Alliance/Telecommunications Industry Association


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Mobile Application Part (MAP)

§MAP resides on top of the SS7 protocol stack.§ It provides procedures for:§ location management§ subscriber data management§ authentication§ call handling§ subscriber tracing§ short message service (SMS) management.


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Mobility procedures in MAP

§MAP handles mobility procedures used to pass mobilesubscriber’s information between switching areas.§When a mobile subscriber roams into a new switching area, its

subscription profile is retrieved from the Home LocationRegister (HLR) using MAP.


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§GPRS OPNET model, used to implement MAP protocol,consists of:§Mobile Station (MS)§ Serving GPRS Support Node (SGSN)§Gateway GPRS Support Node (GGSN)§ Internal HLR§ Sink.

§We already implemented a simplified model with Internal HLRthat did not employ SS7 network (OPNETWORK 2002).§ Instead of MAP, the SGSN used an internal database query to

retrieve subscriber’s data from the Internal HLR.

GPRS model


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MAP implementation

§MAP provides users with a specified set of services. It can beviewed as a “black box” representing a MAP service-provider.§MAP service-user interacts with the MAP service-provider by

issuing or receiving MAP service-primitives.§The MAP service-provider acts as a Transaction Capabilities

Application Part (TCAP) service-user.


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MAP service-primitives

§The MAP services-primitives are classified as:§ common MAP services, available to all MAP service-users§ service-user specific MAP services, specific for particular MAP service-

user.

§Common MAP services perform functions:§ establishing and clearing MAP dialogues between MAP service-users§ invoking services provided by the lower layer§ reporting abnormal situations.


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Common MAP service-primitives

§We implemented the following common MAP services:§MAP-OPEN§MAP-CLOSE§MAP-DELIMITER§MAP-U-ABORT§MAP-P-ABORT§MAP-NOTICE


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Service-user specific MAP services(1)§Service-user specific MAP services perform functions related

to:§mobility management§ location management§ call handling§ packet data protocol (PDP) context activation§ short message service (SMS) management and maintenance.


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Service-user specific MAP services(2)§We implemented only GPRS-related service-user specific

MAP services:§MAP-UPDATE-GPRS-LOCATION§MAP-INSERT-SUBSCRIBER-DATA§MAP-CANCEL-LOCATION§MAP-DELETE-SUBSCRIBER-DATA§MAP-PURGE-MS§MAP-SEND-AUTHENTICATION-INFO§MAP-RESET§MAP-SEND-ROUTING-INFO-FOR-GPRS§MAP-NOTE-MS-PRESENT-FOR-GPRS


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TCAP service-primitives (1)

§MAP protocol relies on the services provided by theTransaction Capabilities Application Part (TCAP).

§MAP services (primitives) are mapped onto correspondingTCAP services.

§ In our model, TCAP service-primitives are sent directly to thepeer because layers below MAP have not been implemented.

§For every implemented service-primitive, a distinct packetformat has been defined in OPNET.


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TCAP service-primitives (2)

§TCAP primitives are divided into:§ dialogue-handling primitives§ component-handling primitives.

§ Implemented dialogue-handling TCAP primitives are:§ TC-BEGIN§ TC-CONTINUE§ TC-END§ TC-U-ABORT

§ Implemented component-handling TCAP primitives are :§ TC-INVOKE§ TC-RESULT-L§ TC-RESULT-NL§ TC-U-ERROR§ TC-U-CANCEL§ TC-U-REJECT


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MAP Protocol Machine

§MAP Protocol Machine (MAP PM) is implemented as acollection of Service State Machines (SSMs) coordinated by aMAP Dialogue State Machine (DSM).§Our model consists of two SSMs: Performing Service State

Machine (PSM) and Requesting Service State Machine (RSM).§All state machines are

implemented in OPNET as finite state machines (FSMs).


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MAP Dialogue State Machine (DSM)

§MAP DSM handles establishment of MAP dialogue betweenone dialogue-initiator and one dialogue-responder.§ MAP DSM process model in OPNET includes eight states:


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§Performing Service State Machine (PSM) handles service-userspecific services invoked by the peer:

§Requesting Service State Machine (RSM) handles service-userspecific services requested by the MAP service-user:

MAP Service State Machines (SSMs)


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Simplifications

§We made following simplifications to the behavior defined inthe MAP specification:§Not implemented: MAP-READY-FOR-SM, MAP-ACTIVATE-

TRACE-MODE, and MAP-DEACTIVATE-TRACE-MODE service-user specific services.

§Not implemented: TC-NOTICE dialogue-handling TC primitive.

§Not implemented: TC-TIMER-RESET, TC-L-REJECT, TC-R-REJECT,and TC-P-ABORT component-handling TC primitives.

§ Implemented only one instance of the PSM and RSM. Hence, only oneMAP service can be handled at a time.


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SGSN node model

§We modified the HLR and SGSN node models in the originalGPRS model.


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HLR node model

§HLR process model above MAP is adapted to act as a MAPservice-user.§The first transmitter-receiver pair is used for communication

with the SGSN.

§The second pair is an optionalinterface with GGSN(not implemented).


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Interaction between SGSN and HLR

§Before a mobile station (MS) can use GPRS services, it mustregister with an SGSN of the GPRS network. This procedure iscalled GPRS attach.§A conceptual description of message exchange during the

attach procedure:


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Message sequence in attachprocedure


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Duration of the attach procedure

§In order to evaluate the influence of MAP signalization onnetwork performance, we measured the processing time of theattach procedure.§The processing time is measured at the MS from the moment

when an Attach Request is sent until an Attach Accept orAttach Reject is received.§The original GPRS model employed a very simple database

query for communication with an internal HLR.§Because of intensive message exchange between MAP entities,

we expected a significant increase in the processing time of theAttach Request .


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§The average duration of the attach procedure in the originalmodel is 77 ms.§The average duration of the attach procedure in the new model

is 100 ms.

Simulation results


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Conclusions

§We described the OPNET implementation of MobileApplication Part (MAP) protocol.

§This implementation has been employed within the GeneralRadio Packet Service (GPRS) network model.

§Services provided by the MAP model are illustrated using anexample that describes the attach procedure in GPRS.

§We observed the processing time of the attach procedure inorder to evaluate the effect of MAP protocol on networkperformance.

§The new GPRS model with MAP implementation has beenuploaded to the OPNET Contributed Model Depot.


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Current and future work

§The existing GPRS model could be further enhanced to fullyutilize services provided by MAP.

§MS and SGSN node models were modified to incorporateLogical Link Control (LLC) protocol (Mikael Johansson).

§Base station model and multiple mobile stations are beingimplemented (Paulman Chan).

§We intend to implement Media Access Control (MAC) layerwith contention resolution.

§We plan to evaluate performance of a GPRS network withmultiple mobile stations, realistic simulation scenarios, andvarious traffic patterns.


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References

[1] Cisco SS7 Fundamentals: http://www.cisco.com/univercd/cc/td/doc/product/tel_pswt/vco_prod/ss7_fund/index.htm (March 2003).

[2] R. Ng and Lj. Trajkovic, “Simulation of general packet radio service network,” OPNETWORK 2002, Washington, DC, August 2002.

[3] 3rd Generation Partnership Project, TS 09.02 v7.12.0, Mobile Application Part (MAP) specification.

[4] ITU-T Q.771, Specifications of Signalling System No. 7, Transaction capabilities application part.

[5] 3rd Generation Partnership Project, TS 03.60 v7.9.0, General Packet Radio Service (GPRS), Service Description.

Documents

OPNETWORK2003 1540 Vukadinovic final editedljilja/ENSC835/Fall03/News/Presentations/talk... · Title: OPNETWORK2003_1540_Vukadinovic_final_edited Author: ljilja Created Date: 9/19/2003